I'm assuming this particular rock was completely outside of everybody's radar. LEO definitely needs more funds, and if they set up distributed computing i'd be happy to donate cpu cycles.

When they come in from a random direction at 19 miles per second, you've got no time to find them. Since the size estimate of this rock was around 10 tons, it's the type of rock that will never be detected by any means until it's in the atmosphere.

And no, it has nothing to do with the asteroid that'll be passing inside the Clarke Belt today. Different orbit all together.

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Captain Ned wrote:When they come in from a random direction at 19 miles per second, you've got no time to find them. Since the size estimate of this rock was around 10 tons, it's the type of rock that will never be detected by any means until it's in the atmosphere.

QFT.

And apparently the largest bomb was only ~500 lbs? That's a lot of mass getting burned and broken off. I can't tell what the "not serious" injuries are that end up totaling 700-800, but I would guess that has more to do with broken glass than getting hit by meteorites and shockwaves.

Spectacular, yes. Deadly, not so much.

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NPR had a great interview with one of the project (I believe) coordinators of the Sentinel Mission. It is a privately funded operation that will be putting a detector in a venus-like orbit around the sun to detect 90% of asteroids 140 meters or greater in size. It will be able to locate a massive amount of objects down to 30 meters.

In the interview the guy said that they have had their first review of the detectors in January, and that the project is on track for a 2017-2018 launch. Their is a lot of good info on the website above

LaChupacabra wrote:NPR had a great interview with one of the project (I believe) coordinators of the Sentinel Mission. It is a privately funded operation that will be putting a detector in a venus-like orbit around the sun to detect 90% of asteroids 140 meters or greater in size. It will be able to locate a massive amount of objects down to 30 meters.

In the interview the guy said that they have had their first review of the detectors in January, and that the project is on track for a 2017-2018 launch. Their is a lot of good info on the website above

... Ok, and if it'll detect an asteroid few miles in diameter, heading straight to Earth, then what? What will be the point of detecting it? Bruce Willis is already too old to do anything

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OK, so this one was big, but not big enough to cause serious devastation. The damage wasn't any worse than that caused by the sort of natural disasters we regularly see from purely terrestrial causes. What's the gap between the size of object we can detect, and the size of object that would cause unprecedented destruction? Can we narrow that gap to zero at a manageable cost? And if so, should we, unless we are also willing to fund technology to deflect at least the smallest of the potential "killer size" objects?

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just brew it! wrote:OK, so this one was big, but not big enough to cause serious devastation.

500 kilotons not big enough? The only reason those dash-cam vids got uploaded and Chelyabinsk is still around is the height of the explosion (30-50 km under current estimates). If that thing holds together into the lower atmosphere and explodes at 10km there would have been serious devastation. Given its velocity (18 km/sec per NASA) and impact angle (15 degrees seems to be the consensus estimate), my rusty trig (and I'm not even going to attempt spherical trig) tells me that 18km/sin 15 degrees = 4.66 km altitude loss per second. That give a range of 4.3 to 8.6 additional seconds of flight time to get to a 10km burst altitude. No, those people got off extremely lucky.

ChronoReverse wrote:That's a little misleading since the 500kt is the total energy released over the entire event.

OK, say 250kt at 10km. Still a Bad Day.

Unfortunately, none of the web-based blast calculators I can find allow you to set the blast altitude. It takes about 1 PSI overpressure (blast wave) to blow out windows like we saw in the vids. At 5 PSI overpressure, most of those buildings would have been blown down. Since I'm not a weaponeer, I don't know the right math to calculate the change in overpressure caused by a potential reduction in blast altitude.

He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.

just brew it! wrote:OK, so this one was big, but not big enough to cause serious devastation.

500 kilotons not big enough?

No deaths (as far as we know so far). Damage seems to be limited to blown out windows and the like. I would say it did not cause "serious devastation".

And the point I'm trying to make is that another 5 seconds of flight time and we'd most likely be charting many deaths. We got lucky. This rock had the potential to cause massive damage, and that's all I'm trying to get across.

He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.

Who knows. The air is thicker down low so a different angle could have resulted in an entirely different pattern of breakup. If it had come straight down for instance, it might not have had time to explode at all. Or it could have exploded just at the optimal height for maximum airburst damage.

For 0.5MT you get 4.6psi at 5.7km. Air blasts are inverse cube root right? So that would put 12km close to 1psi?

Just like all of the calculators I googled it assumes optimum burst height, which is defined as the height that produces the greatest area of 10 PSI overpressure. Any potential blast we're talking about here is well above optimum, meaning a smaller 10 PSI area. What I'd really like to be able to model are the 5 PSI curves for varying blast heights in the range of 250-500 kt.

He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.

just brew it! wrote:To get an accurate picture wouldn't you also need to account for the fact that an asteroid/meteor doesn't explode the same way TNT does? Or is that already accounted for in the 500 kT estimate?

My guess is that the 500 kT is simply blast effect comparison. Radiation effects are right out. Blast overpressures shouldn't be too far off, and I'd expect thermal effects to be quite reduced from nuclear effects due to the lack of the multi-million degree fireball. The blast overpressures are what I'm most curious about as they'll be the key damage component for an air-burst rock.

Given the wide area over which windows were broken there was clearly a very large 1 PSI overpressure area. Don't know if there was any way to measure max overpressure directly below the hypocenter through dash-cam or security cam footage. It'll probably get sussed out over the next few weeks as the custodians of big bangs look through all the data they can gather given that they can no longer test big bangs, especially above-ground.

He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.

For 0.5MT you get 4.6psi at 5.7km. Air blasts are inverse cube root right? So that would put 12km close to 1psi?

Just like all of the calculators I googled it assumes optimum burst height, which is defined as the height that produces the greatest area of 10 PSI overpressure. Any potential blast we're talking about here is well above optimum, meaning a smaller 10 PSI area. What I'd really like to be able to model are the 5 PSI curves for varying blast heights in the range of 250-500 kt.

Yeah =/

I'm still skeptical that the explosion sound is actually the blastwave of the explosion though. The ranges here are so far off that it seems rather unlikely. For example, in one of the videos with the blast breaking glass, there's about 30 seconds between flash and the boom so that's 10km. But we know the meteor exploded 30km over the earth and this video is from a distance making it even more than 30km.